1. Field of the Invention
The present invention relates to an electronic device unit including a plurality of board-side terminals formed at an end portion of the circuit board, and being configured to carry out electrical connection to an external device by bringing contact terminals, which are fixed to a connector housing mounted on the circuit board in a removable manner, into contact with the board-side terminals. In particular, the present invention relates to an improvement of an electronic device unit for the purpose of suppressing sliding wear of a conductive contact surface along with insertion and removal of such a card edge connector.
2. Description of the Related Art
In an electronic device unit configured such that board-side terminals each formed of a copper foil pattern formed at an end portion of a circuit board are connected to an external device through intermediation of a card edge connector connected to a wire harness or mounted on a wiring board, various approaches have been made to suppress sliding wear of a conductive contact surface along with insertion and removal of such a card edge connector.
For example, referring to FIG. 1 of a “card edge connector” disclosed in Japanese Patent Application Laid-open No. 2001-155829 (FIG. 1, Abstract, paragraph [0028]), a card-edge type printed board 10 corresponding to the circuit board of the present invention is removably connected, through intermediation of a card edge connector 30, to a connection-target printed board 20 corresponding to an external connection conductor of the present invention. The card edge connector 30 includes a fixed-side connector housing 31 having first contact pins 35, and a pivot-side connector housing 32 having second contact pins 36 and being pivotably supported on pivot portions 33 by engagement portions 34. The first and second contact pins 35 and 36 are brought into contact with the front and back of a pad 11 (board-side terminal of the present invention) formed on the card-edge type printed board 10, and a distal end portion 37 of each second contact pin 36 is brought into sliding contact with a pad 21 formed on the connection-target printed board 20.
The second contact pin 36 has spring property, and hence the pivot-side connector housing 32 in a normal state is separated away from the fixed-side connector housing 31. When the card-edge type printed board 10 is inserted, the card-edge type printed board 10 presses an abutment portion 38 formed at a lower part of the pivot-side connector housing 32, to thereby pivot the pivot-side connector housing 32. In this manner, the pivot-side connector housing 32 and the fixed-side connector housing 31 sandwich the card-edge type printed board 10 therebetween. As a result, it is possible to attain a card edge connector excellent in operability of the insertion and removal of the card-edge type printed board and also excellent in durability without damage to the respective components at the time of the insertion and removal of the card-edge type printed board.
In contrast, referring to FIGS. 1, 4, and 5 of an “electronic device” disclosed in Japanese Patent Application Laid-open No. 2012-151005 (FIG. 1, Abstract, paragraphs [0031] and [0037]), electrodes 12a and 12b are formed on the front and back of an electronic board 10 having an end portion 11 exposed from a case 50. A card edge connector 40 includes a pair of opposing portions 22 and 23 held by a coupling portion 24 so as to be pivotable relative to each other, and biased in a closing direction by a ring-shaped spring portion 25 (see FIG. 3). The pair of opposing portions 22 and 23 includes first terminals 30a and second terminals 30b to which end portions of a harness (not shown) are fixed.
When the card edge connector 40 is inserted to the electronic board 10, the opposing portions 22 and 23 are separated away from each other by a pair of protrusions 27 formed on the opposing portions 22 and 23 (see FIG. 4), and then the pair of protrusions 27 is fitted to a recess 13 formed in the electronic board 10 so that contact portions 31a and 31b of the first and second terminals 30a and 30b are brought into contact with the electrodes 12a and 12b of the electronic board 10.
Thus, the electronic board 10 is inserted under a state in which the contact portions 31a and 31b and the electronic board 10 are out of contact with each other, thereby suppressing such a risk that the electrical connection between the first and second terminals 30a and 30b and the electrodes 12a and 12b fails due to stripping of plating of the contact portions 31a and 31b and adhesion of components of the electronic board 10 onto the contact regions of the contact portions 31a and 31b.
On the other hand, referring to FIGS. 1 and 6 of an “electronic device” disclosed in Japanese Patent Application Laid-open No. 2013-118158 (FIG. 1, Abstract, paragraph [0083]), electrodes 60 are formed on the front and back of a circuit board 12 having an end portion exposed from a case 13. Terminals 30 each connected to one end of a harness 14 are formed in a housing 20 of a card edge connector 11.
A slider 40 to be retreated by pressing from an end surface of the circuit board 12 is provided in an insertion hole 21 of the housing 20. The upper and lower terminals 30 initially compressed by slope surfaces of a trapezoid of the slider 40 are separated away from each other so as to sandwich the circuit board 12 along with the retreat of the slider 40. Then, contact portions 31 of the terminals 30 are brought into contact with the electrodes 60 of the circuit board 12.
Thus, even when the circuit board is repeatedly inserted to and removed from the card edge connector, the reliability of electrical connection can be enhanced as compared to the related art. When the circuit board is inserted to or removed from the card edge connector, there is no such risk that the terminal is damaged or deformed as in the case where a plating layer formed on the surface of the terminal is stripped off due to contact of the contact portion of the terminal with an edge or an electrode forming surface of the circuit board. Further, there is no such risk that short circuit occurs due to, for example, plating chips that are stripped off.
Further, the contact portion 31 is slightly slid along the surface of the electrode 60, thereby being capable of securing a wiping distance for stripping an insulation coating formed on the surface of the electrode 60 and removing foreign matters on the surface.
Further, referring to FIGS. 2 of a first embodiment of a “connector” disclosed in Japanese Utility Model Application Laid-open No. Hei 03-050783 (FIGS. 2 and 3, Scope of Claims for Utility Model Registration), a plurality of connector-side contacts 3 are integrated by a movable mold 4a, and the movable mold 4a is moved at the inside of a connector main body 1a by pressing from an end surface of a printed board 6. As a result, the connector-side contacts 3 are brought into pressure contact with board-side contacts 7 (FIG. 1) by a constriction portion 1c formed in the connector main body 1a.
Further, referring to FIGS. 3 of a second embodiment, the plurality of connector-side contacts 3 are fixed to a connector main body 1b, and a movable mold 4b, which is movable at the inside of the connector main body 1b, is moved at the inside of the connector main body 1b by pressing from the end surface of the printed board 6. As a result, the connector-side contacts 3 are brought into pressure contact with the board-side contacts 7 (FIG. 1) by a constriction portion 4c formed in the movable mold 4b.
In any case, when the printed board 6 is removed, each of the movable molds 4a and 4b is pushed back by a spring 5 so that the connector-side contacts 3 and the board-side contacts 7 are separated from each other.
According to Japanese Patent Application Laid-open No. 2001-155829 (FIG. 1, Abstract, paragraph [0028]), the second contact pin 36 formed on the pivot-side connector housing 32 is connected in series to the pad 11 on the card-edge type printed board 10 side and the pad 21 on the connection-target printed board 20 side. Therefore, there are problems in that the contact reliability is degraded, and that sliding wear of the contact surface occurs due to sliding friction between the pad 21 on the connection-target printed board 20 side and the distal end portion 37 of the second contact pin 36 along with opening and closing operations for the pivot-side connector housing 32.
Further, the contact pressure between the first and second contact pins 35 and 36 and the pad 11 of the card-edge type printed board 10 in a closed state of the pivot-side connector housing 32 is determined based on a pressing force of the card-edge type printed board 10 for pressing the abutment portion 38 formed at the lower part of the pivot-side connector housing 32. This pressing force exhibits a value equal to or less than a value of the contact friction resistance between the first and second contact pins 35 and 36 and the pad 11 of the card-edge type printed board 10. Therefore, there is a problem in that no sufficient pressing force can be obtained.
According to Japanese Patent Application Laid-open No. 2012-151005 (FIG. 1, Abstract, paragraphs [0031] and [0037]), in order to remove the electronic board 10 inserted to the card edge connector 40, it is essential to reduce the inclination of the protrusions 27 fitted to the recess 13 of the electronic board 10. With the reduced inclination, at the time of insertion of the electronic board 10, the amount of insertion movement of the electronic board 10 becomes larger during a period in which the protrusions 27 of the opposing portions 22 and 23 start to be fitted to the recess 13 of the electronic board 10 and then the fitting of the protrusions 27 is completed. Therefore, there is a problem in that, during this period, the amount of sliding friction movement of the contact portions 31a and 31b of the first and second terminals 30a and 30b and the electrodes 12a and 12b of the electronic board 10 becomes larger.
Further, the pair of opposing portions 22 and 23 biased in the closing direction by the ring-shaped spring portion 25 is held by the coupling portion 24 so as to be pivotable relative to each other, and hence a bending force is generated at the end portions of the harness (not shown). Therefore, there is a problem in that the harness is disconnected and the pivoting torque of the coupling portion 24 becomes unstable.
According to Japanese Patent Application Laid-open No. 2013-118158 (FIG. 1, Abstract, paragraph [0083]), during a transition period in which the contact portions 31 of the terminals 30 start to be brought into contact with the electrodes 60 of the circuit board 12 and then the retreat of the slider 40 is completed, the sliding friction occurs between the contact portions 31 and the electrodes 60 so that oxide films formed on the contact surfaces can be removed. However, there is a problem in that the contact surfaces are worn when no oxide film is formed.
Note that, in order to reduce the amount of sliding friction movement, it is only necessary that the gradient of a support surface 41 of the slider 40 be increased. In this case, however, there is a problem in that the slider 40 is difficult to move forward to the initial position when the circuit board 12 is removed.
Further, according to Japanese Utility Model Application Laid-open No. Hei 03-050783 (FIGS. 2 and 3, Scope of Claims for Utility Model Registration), in the first embodiment illustrated in FIGS. 2, the sliding friction does not occur between the connector-side contacts 3 and the board-side contacts 7, but the connector-side contacts 3 need to move at the inside of the connector main body 1a along with insertion and removal of the printed board 6. Therefore, there is a problem in that lead wires 2a are damaged due to bending, and that waterproofing is difficult to carry out.
Note that, in the second embodiment illustrated in FIGS. 3, in the process of pressing the connector-side contacts 3 against the board-side contacts 7 by the constriction portion 4c, the sliding friction occurs between the connector-side contacts 3 and the board-side contacts 7. Therefore, there is a problem in that the sliding wear occurs similarly when the printed board 6 is removed.